Recent seismic events occurred around the world have highlighted the great vulnerability of existing buildings stock. In particular, many structures in the Italian territory are designed without seismic criteria, showing significant damage after recent earthquakes, causing many casualties and great economic losses. Earthquake impact assessment has become one of the most investigated topics by several research groups and within national and international projects. In Italy, for example, the National Department of Civil Protection has allocated several economic funds within the ReLUIS project to define methodologies able to support the decision-making process for seismic prevention activities and risk reduction.

This work aims to assess economic losses using the methodology proposed by FEMA-P58, according to Performance-Based Earthquake Engineering (PBEE) method, evaluating the influence of bi-directional ground motion on loss estimates. The analyzed case study is a three-dimensional non-linear frame characterized by weak and strong seismic directions and modeled using OpenSees software. The model considers the joint deformability and the flexural and shear behavior of beams and columns. Thirty time-histories analyses were performed considering bi-directional ground motions applied in the two main directions of the buildings employing the greater spectral acceleration firstly in the weak structural direction and then in the strong one. Eight increasing hazard levels were selected for the non-linear time-history analyses, and the structural analysis results, in terms of interstory drift ratio and peak floor acceleration, were implemented for loss assessment. The results are discussed in terms of expected annual losses and loss hazard curves.